Positive resist composition and patterning process

ABSTRACT

A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising recurring units containing a non-leaving hydroxyl group represented by formula (1) wherein R 1  is H, methyl or trifluoromethyl, m is 1 or 2, and the hydroxyl group attaches to a tertiary carbon atom. The composition is improved in resolution when processed by lithography.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2008-227727 filed in Japan on Sep. 5, 2008,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a positive resist composition for themicropatterning technology which is improved in resolution, patterndensity dependency and mask fidelity, and a patterning process using thesame.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, it is desired to miniaturize the pattern rule. Great effortshave been devoted for the development of the micropatterning technologyusing deep-ultraviolet (deep-UV) or vacuum-ultraviolet (VUV)lithography. The photolithography using KrF excimer laser (wavelength248 nm) as the light source has already established the main role in thecommercial manufacture of semiconductor devices. The photolithographyusing ArF excimer laser (wavelength 193 nm) has commenced commercialmanufacture as the advanced microprocessing process. In the ArF excimerlaser lithography, a further improvement in resist material performanceis strongly demanded to enable a further extension of resolution,partially because the succeeding technology remains uncertain. Effortshave also been made on the development of the immersion lithographydesigned to extend the resolution by interposing a high refractive indexliquid between a resist coating and a projection lens, and a resistmaterial suited for the immersion lithography is thus needed.

The requisite properties for the resist materials adapted for the ArFexcimer laser lithography include transparency at wavelength 193 nm anddry etch resistance. Resist materials comprising as a base resinpoly(meth)acrylic acid derivatives having bulky acid-labile protectivegroups as typified by 2-ethyl-2-adamantyl and 2-methyl-2-adamantylgroups were proposed as having both the properties (JP-A 9-73173 andJP-A 9-90637). Since then, a variety of materials have been proposed.Most of them commonly use resins having a highly transparent main chainand a carboxylic acid moiety protected with a bulky tertiary alkylgroup.

While the prior art resist materials for the ArF excimer laserlithography suffer from several problems, a decline of resolution byover-diffusion of the acid generated by the photoacid generator is aserious problem. In the ArF excimer laser lithography, the acidgenerated upon exposure triggers deprotection reaction on the base resinwhich proceeds during heat treatment following exposure (post-exposurebake or PEB). Movement or diffusion of the acid occurs during PEB. Sincechemically amplified resist materials depends on the function of theacid to act as a catalyst to promote deprotection reaction, moderateacid movement is necessary. However, acid movement degrades an opticalimage, indicating that excess acid movement detracts from resolution. Tocomply with the outstanding demands for a further size reduction in theArF excimer laser lithography including and a higher resolution due to agood command of the immersion lithography, there is a need for a resistmaterial featuring controlled acid movement and higher resolutioncapability.

CITATION LIST

-   Patent Document 1: JP-A H09-73173-   Patent Document 2: JP-A H09-90637-   Patent Document 3: U.S. Pat. No. 6,391,520 (JP-A 2000-122295)

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a positive resist compositionwhich exhibits a high resolution, improved pattern density dependencyand mask fidelity when processed by the photolithography using ArFexcimer laser light as a light source, and a patterning process usingthe same.

The inventors have found that a positive resist composition comprising apolymer comprising specific recurring units as a base resin displays anexcellent resolution capability when processed by photolithography. Thecomposition is thus quite effective for precise micropatterning.

The invention provides a positive resist composition and a patternforming process as defined below.

In one aspect, the invention provides a positive resist compositioncomprising (A) a resin component which becomes soluble in an alkalinedeveloper under the action of an acid and (B) a compound capable ofgenerating an acid in response to actinic light or radiation. The resincomponent (A) is a polymer comprising recurring units containing anon-leaving hydroxyl group, represented by the general formula (1).

Herein R¹ is hydrogen, methyl or trifluoromethyl, and m is 1 or 2, withthe proviso that the number “m” of hydroxyl groups each attach to atertiary carbon atom.

In a preferred embodiment, the polymer as resin component (A) furthercomprises recurring units of the general formulae (2) and (3).

Herein R¹ is each independently hydrogen, methyl or trifluoromethyl, R²is an acid labile group, and R³ is a group containing a 5- or 6-memberedlactone ring as a partial structure.

In a preferred embodiment, the compound (B) is a sulfonium salt compoundhaving the general formula (4).

Herein R⁴, R⁵ and R⁶ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom, R⁷ is a straight, branched or cyclic,monovalent hydrocarbon group of 7 to 30 carbon atoms which may contain aheteroatom, and R⁸ is hydrogen or trifluoromethyl.

In one aspect, the invention provides a process for forming a pattern,comprising the steps of applying the positive resist composition definedabove onto a substrate to form a resist coating; heat treating theresist coating and exposing it to high-energy radiation or electron beamthrough a photomask; heat treating the exposed coating and developing itwith a developer. In one preferred embodiment, the exposing step iseffected by the immersion lithography wherein a high refractive indexliquid having a refractive index of at least 1.0 intervenes between theresist coating and a projection lens. In another preferred embodiment,the process further comprises the step of applying a protective coatingon the resist coating, and the exposing step is effected by theimmersion lithography wherein a high refractive index liquid having arefractive index of at least 1.0 intervenes between the protectivecoating and a projection lens.

ADVANTAGEOUS EFFECT OF INVENTION

The positive resist composition of the invention exhibits asignificantly high resolution when processed by the micropatterningprocess, especially ArF lithography. The composition is thus quiteeffective for precise micropatterning.

DESCRIPTION OF EMBODIMENTS

Below the resist composition of the invention is described in detail.The singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise. The notation (Cn-Cm) means agroup containing from n to m carbon atoms per group.

It is understood that for some structures represented by chemicalformulae, there can exist enantiomers and diastereomers because of thepresence of asymmetric carbon atoms. In such a case, a single formulacollectively represents all such isomers. The isomers may be used aloneor in admixture.

The resist composition of the invention comprises (A) a resin componentwhich becomes soluble in an alkaline developer under the action of anacid, and (B) a compound capable of generating an acid in response toactinic light or radiation, wherein resin component (A) is a polymer orhigh-molecular weight compound comprising recurring units containing anon-leaving hydroxyl group, represented by the general formula (1).

Herein R¹ is hydrogen, methyl or trifluoromethyl, and m is 1 or 2, withthe proviso that the number “m” of hydroxyl groups each attach to atertiary carbon atom.

As the base resin in resist compositions for the ArF excimer laserlithography, resins having incorporated (meth)acrylate units having a3-hydroxyadamantan-1-yl or 3,5-dihydroxyadamantan-1-yl group as shownbelow are widely used.

By introducing these recurring units into resins, the movement of theacid generated upon exposure is controlled appropriate so that theresolution capability may be improved. Although the mechanism is notwell understood, it is surmised that hydroxyl groups on these unitsrepeat capture and release of proton whereby acid diffusion iscontrolled. Since these hydroxyl groups are at the bridgehead positionsof adamantane ring, they are not eliminated by dehydration reaction anda proton capture ability is never lost. This is also an advantage of thestructure.

Based on the hypothetical acid diffusion controlling mechanism of3-hydroxyadamantan-1-yl (meth)acrylate and 3,5-dihydroxyadamantan-1-yl(meth)acrylate, the inventors tried to design recurring units having agreater acid diffusion controlling effect. It has been found that thoseunits satisfying the following requirements 1) to 3) are compliant withthe object.

-   1) To introduce a non-leaving hydroxyl group for the purpose of    imparting a proton capture ability.-   2) To place a hydroxyl group at a position spaced appropriately    apart from the main chain via a linking group, for the purpose of    enhancing the proton capture effect. The increased distance from the    main chain increases the probability of contact between hydroxyl    group and proton, with an improvement in proton capture ability    being expectable. The introduction of the linking group allows for    an appropriate freedom of movement, which also enhances the proton    capture effect.-   3) To introduce a robust adamantane ring structure in the link    between the main chain and the hydroxyl group for the purpose of    densifying a resist film to control acid diffusion. This prevents    embedment of hydroxyl group in proximity to the main chain and    reduces the free volume of a resist film to achieve controlled acid    movement.

Most preferred among those units satisfying requirements 1) to 3) arerecurring units containing a non-leaving hydroxyl group, represented byformula (1). Exemplary recurring units of formula (1) are illustratedbelow.

Herein, the wavy line indicates an indefinite direction of the bond. Thesame applies hereinafter.

In the foregoing examples, the bond position of a hydroxyl group is on acarbon atom at the bridgehead of adamantane ring or on a carbon atomhaving introduced a linking group to the main chain. In the former case,since a double bond cannot be formed within the adamantane ring despitethe presence of hydrogen atoms on adjacent carbon atoms, elimination ofa hydroxyl group by dehydration reaction cannot occur. In the lattercase, although it seems that dehydration reaction may occur because ofthe presence of hydrogen atom on adjacent carbon atom outside the ring,reaction of dehydrating hydroxyethyl ester into vinyl ester does hardlyproceed in fact, and thus elimination of a hydroxyl group by dehydrationreaction does not occur in a substantial sense. When the above-mentionedrecurring units having both a non-leaving hydroxyl group capable ofexerting an acid diffusion controlling effect and a linking group forenhancing the effect are introduced into a base resin, a resistcomposition having high resolution, improved pattern density dependency(or optical proximity effect), and mask fidelity may be formulatedtherefrom.

In the resin component (A) which becomes soluble in an alkalinedeveloper under the action of an acid, the recurring units containing anon-leaving hydroxyl group, represented by formula (1), are introducedin an amount of 1 to 50 mol %, preferably 5 to 40 mol %, and morepreferably 10 to 30 mol %, provided that the total of entire recurringunits is 100 mol %. Although values outside the range need not bepositively excluded, a balance of properties required of the resistmaterial may be disrupted at outside values.

Prior to the present invention, Patent Document 3 (U.S. Pat. No.6,391,520, JP-A 2000-122295) discloses recurring units possessing anadamantane ring having a non-leaving hydroxyl group introduced thereinand a linking group. In Patent Document 3, hydroxyl and other polarfunctional groups are introduced for the only purpose of mitigating thehydrophobicity of adamantane ring. With respect to the linking group, itis described nowhere why it is introduced or how it works. By contrast,making investigations on the type and position of a functional group tobe introduced and the structure of a linking group for the purpose ofimproving the acid diffusion controlling effect, the inventors havecompleted the present invention. Additionally, as a consequence, aconstruction different from the construction illustrated as preferredembodiment in Patent Document 3 is selected. It is believed that sincethe present invention has an object and effect different from those ofPatent Document 3, employs a construction different from that of PatentDocument 3 in a substantial sense, and achieves different results ofsignificance, the present invention is not obvious over Patent Document3.

In the resist composition of the invention, the resin component (A)which becomes soluble in an alkaline developer under the action of anacid is preferably a polymer further comprising recurring units of thegeneral formulae (2) and (3).

Herein R¹ is each independently hydrogen, methyl or trifluoromethyl, R²is an acid labile group, and R³ is a group containing a 5- or 6-memberedlactone ring as a partial structure.

The acid labile group represented by R² may be selected from a varietyof such groups to be deprotected with the acid generated from thephotoacid generator to be described later. It may be any of well-knownacid labile groups commonly used in prior art resist compositions,especially chemically amplified resist compositions. Examples of theacid labile group are groups of the following general formulae (L1) to(L4), tertiary alkyl groups of 4 to 20 carbon atoms, preferably 4 to 15carbon atoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.

Herein, the broken line denotes a valence bond. In formula (L1), R^(L01)and R^(L02) are hydrogen or straight, branched or cyclic alkyl groups of1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, n-octyl, andadamantyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a heteroatomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and substituted forms of such alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples of thestraight, branched or cyclic alkyl groups are as exemplified above forR^(L01) and R^(L02), and examples of the substituted alkyl groups are asshown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with carbon and oxygen atoms towhich they are attached. Each of R^(L01), R^(L02) and R^(L03) is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,2-(tricyclo[5.2.1.0^(2,6)]decan-8-yl)propan-2-yl,2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecan-3-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,8-methyl-8-tricyclo[5.2.1.0^(2,6)]decyl,8-ethyl-8-tricyclo[5.2.1.0^(2,6)]decyl,3-methyl-3-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecyl,3-ethyl-3-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecyl, and the like.Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter y is aninteger of 0 to 6.

In formula (L3), R^(L05) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of the optionally substituted alkyl groupsinclude straight, branched or cyclic alkyl groups such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl, and bicyclo[2.2.1]heptyl, andsubstituted forms of such groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups or inwhich some methylene groups are replaced by oxygen or sulfur atoms.Examples of optionally substituted aryl groups include phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m isequal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or3.

In formula (L4), R^(L06) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms. Exemplaryhydrocarbon groups are straight, branched or cyclic alkyl groups such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl, and substitutedforms of these groups in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups. Alternatively, two ofR^(L07) to R^(L16) may bond together to form a ring with the carbonatom(s) to which they are attached (for example, a pair of R^(L07) andR^(L08), R^(L07) and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10),R^(L11) and R^(L12), R^(L13) and R^(L14), or a similar pair form aring). Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group when they form a ring, examples of which are thoseexemplified above for the monovalent hydrocarbon groups, with onehydrogen atom being eliminated. Two of R^(L07) to R^(L16) which areattached to vicinal carbon atoms may bond together directly to form adouble bond (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair).

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxybutyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 1-methyl-2-cyclopentenyl, 1-ethyl-2-cyclopentenyl,1-methyl-2-cyclohexenyl, and 1-ethyl-2-cyclohexenyl groups.

Of the acid labile groups of formula (L4), those groups of the followingformulae (L4-1) to (L4-4) are preferred.

In formulas (L4-1) to (L4-4), the broken line denotes a bonding site anddirection. R^(L41) is each independently a monovalent hydrocarbon group,typically a straight, branched or cyclic C₁-C₁₀ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane structure as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Illustrative examples of the acid labile group of formula (L4) are givenbelow.

Examples of the tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkylgroups are as exemplified for R^(L04) and the like.

In the resin component (A) which becomes soluble in an alkalinedeveloper under the action of an acid, the recurring units having anacid labile group, represented by formula (2), are introduced in anamount of 5 to 80 mol %, preferably 10 to 70 mol %, and more preferably15 to 65 mol % provided that the total of entire recurring units is 100mol %. Although values outside the range need not be positivelyexcluded, a balance of properties required of the resist material may bedisrupted at outside values.

R³ is a group containing a 5- or 6-membered lactone ring as a partialstructure, examples of which are illustrated below, but not limitedthereto.

In the resin component (A) which becomes soluble in an alkalinedeveloper under the action of an acid, the recurring units having a 5-or 6-membered lactone ring, represented by formula (3), are introducedin an amount of 5 to 80 mol %, preferably 10 to 70 mol %, and morepreferably 15 to 65 mol %, provided that the total of entire recurringunits is 100 mol %. Although values outside the range need not bepositively excluded, a balance of properties required of the resistmaterial may be disrupted at outside values.

In addition to the non-leaving hydroxyl group-containing recurring unitsof formula (1), the acid labile group-containing recurring units offormula (2), and the 5- or 6-membered lactone ring-containing recurringunits of formula (3), the resin component (A) which becomes soluble inan alkaline developer under the action of an acid may further compriseadditional recurring units in an amount of 0 to 50 mol %, and preferably0 to 40 mol %, provided that the total of entire recurring units is 100mol %.

Exemplary preferred constructions of resin component (A) are givenbelow, but not limited thereto.

The polymer as resin component (A) should preferably have a weightaverage molecular weight (Mw) of 1,000 to 50,000, and more preferably2,000 to 30,000, as measured by gel permeation chromatography (GPC)versus polystyrene standards.

The polymer as resin component (A) may be obtained throughcopolymerization of (meth)acrylate derivative monomers corresponding tothe respective recurring units by any well-known technique such asradical polymerization. It is noted that the polymers used in Examplesto be described later were synthesized from preselected (meth)acrylatederivative monomers by a standard radical polymerization technique.

In a preferred embodiment, the compound (B) capable of generating anacid in response to actinic light or radiation is a sulfonium saltcompound having the general formula (4):

wherein R⁴, R⁵ and R⁶ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom, R⁷ is a straight, branched or cyclic,monovalent hydrocarbon group of 7 to 30 carbon atoms which may contain aheteroatom, and R⁸ is hydrogen or trifluoromethyl.

Use of a sulfonium salt having formula (4) as an acid generator iseffective in controlling acid diffusion and improving resolutioncapability. Upon exposure, the compound of formula (4) generates afluoroalkanesulfonic acid, whose mobility is substantially restraineddue to a bulky partial structure and a polar group, as compared withsimple perfluoroalkanesulfonic acids such as nonafluorobutanesulfonicacid. Accordingly, a polymer comprising non-leaving hydroxylgroup-containing recurring units of formula (1) may be used, preferablyin combination with an acid generator of formula (4), to formulate aresist composition which is characterized by effectively controlled aciddiffusion and capable of forming a pattern faithful to an optical image.

Below the compound (B) capable of generating an acid in response toactinic light or radiation is further illustrated. In formula (4), R⁴,R⁵ and R⁶ are each independently hydrogen or a straight, branched orcyclic, monovalent hydrocarbon group of 1 to 20 carbon atoms which maycontain a heteroatom(s). Exemplary hydrocarbon groups include methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl, and butyladamantyl, and modified forms of the foregoingin which any carbon-carbon bond is separated by a hetero atomic groupsuch as —O—, —S—, —SO—, —SO₂—, —NH—, —C(═O)—, —C(═O)O— or —C(═O)NH— orin which any hydrogen atom is substituted by a functional group such as—OH, —NH₂, —CHO, or —CO₂H. R⁷ is a straight, branched or cyclic,monovalent hydrocarbon group of 7 to 30 carbon atoms which may contain aheteroatom(s), examples of which are given below, but not limitedthereto.

Note that the broken line denotes a valence bond. R⁸ is hydrogen ortrifluoromethyl.

Exemplary preferred constructions of the acid generator (B) are givenbelow, but not limited thereto.

Other Resin Component

In addition to resin component (A) or polymer comprising non-leavinghydroxyl group-containing recurring units of formula (1), the resistcomposition of the invention may further comprise another resincomponent.

The resin component other than resin component (A) that can be added tothe resist composition includes, but is not limited to, polymerscomprising units of the following formula (R1) and/or (R2) and having aweight average molecular weight of 1,000 to 100,000, especially 3,000 to30,000, as measured by GPC versus polystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group,examples of which include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl,cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl,butylcyclohexyl, adamantyl, ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbonatoms having at least one group selected from among fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups. Examplesinclude hydrogen, carboxyethyl, carboxybutyl, carboxycyclopentyl,carboxycyclohexyl, carboxynorbornyl, carboxyadamantyl, hydroxyethyl,hydroxybutyl, hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl,hydroxyadamantyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyl, andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]-cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a carboxyl group or a monovalenthydrocarbon group of 1 to 15 carbon atoms having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups while the remaining R's independently represent hydrogenor straight, branched or cyclic C₁-C₁₅ alkyl groups. Examples ofsuitable monovalent C₁-C₁₅ hydrocarbon groups having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups include carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl,hydroxyadamantyloxycarbonyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclo-hexyloxycarbonyl,andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclo-hexyloxycarbonyl.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

Two of R⁰⁰⁵ to R⁰⁰⁸ (for example, a pair of R⁰⁰⁵ and R⁰⁰⁶, R⁰⁰⁶ andR⁰⁰⁷, or R⁰⁰⁷ and R⁰⁰⁸) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofring-forming R⁰⁰⁵ to R⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15carbon atoms having at least one group selected from fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups, while theremaining R's are independently single bonds, hydrogen atoms orstraight, branched or cyclic C₁-C₁₅ alkyl groups. Suitable divalentC₁-C₁₅ hydrocarbon groups having at least one group selected fromfluorinated substituent groups, carboxyl groups and hydroxyl groupsinclude those exemplified above as the monovalent hydrocarbon groupshaving at least one group selected from fluorinated substituent groups,carboxyl groups and hydroxyl groups, with one hydrogen atom eliminatedtherefrom. Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups areas exemplified for R⁰⁰³.

R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbon atomscontaining a —CO₂— partial structure. Examples include 2-oxooxolan-3-yl,4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl,2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of 2 to15 carbon atoms containing a —CO₂— partial structure, while theremaining R's are independently hydrogen atoms or straight, branched orcyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitable monovalentC₂-C₁₅ hydrocarbon groups containing a —CO₂— partial structure include2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Suitable straight, branched orcyclic C₁-C₁₅ alkyl groups are as exemplified for R⁰⁰³.

Two of R⁰¹⁰ to R⁰¹³ (for example, a pair of R⁰¹⁰ and R⁰¹¹, R⁰¹¹ andR⁰¹², or R⁰¹² and R⁰¹³) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofring-forming R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR's are independently single bonds, hydrogen atoms or straight, branchedor cyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitabledivalent C₁-C₁₅ hydrocarbon groups containing a —CO₂— partial structureinclude 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas those exemplified as the monovalent hydrocarbon groups containing a—CO₂— partial structure, with one hydrogen atom eliminated therefrom.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing such a polycyclic hydrocarbon group. Examplesinclude norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, norbornylmethyl, and adamantylmethyl as well as alkyl- orcycloalkyl-substituted forms of the foregoing. R⁰¹⁵ is an acid labilegroup as illustrated for R².

R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight, branched or cyclic C₁-C₈alkyl group, examples of which include methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl and cyclohexyl.

X is CH₂ or an oxygen atom. Letter k is 0 or 1.

In formulae (R1) and (R2), letters a1′, a2′, a3′, b1′, b2′, b3′, c1′,c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1,satisfying a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′,h′, i′, j′, o′, and p′ are numbers from 0 to less than 1, satisfyingf′+g′+h′+i′+j′+o′+p′=1; x′, y′ and z′ are each an integer of 0 to 3,satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3.

With respect to the recurring units of formula (R1) and (R2), units ofmore than one type may be incorporated at the same time. Incorporationof units of more than one type enables to adjust the performance of aresist material in which the resulting polymer is formulated.

Understandably, the sum of respective units=1 means that in a polymercomprising recurring units, the total of the indicated recurring unitsis 100 mol % relative to the total of entire recurring units.

Examples of the recurring units incorporated at compositional ratio a1′in formula (R1) and the recurring units incorporated at compositionalratio f′ in formula (R2) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′in formula (R1) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′in formula (R1) and the recurring units incorporated at compositionalratio g′ in formula (R2) are given below, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a1′, b1′, c1′, and d1′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a2′, b2′, c2′, d2′ and e′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a3′, b3′, c3′, and d3′ in formula (R1) are shownbelow, but not limited thereto.

Examples of polymers having formula (R2) are shown below, but notlimited thereto.

The other polymer is blended in an amount of preferably 0 to 80 parts,more preferably 0 to 60 parts, and even more preferably 0 to 50 parts byweight, provided that the total of the resin component (A) and the otherpolymer is 100 parts by weight. When blended, the amount of the otherpolymer is preferably at least 20 parts, more preferably at least 30parts by weight. Too much amounts of the other polymer may prevent theresin component (A) from exerting its own effect, probably resulting ina lower resolution and degraded pattern profile. The other polymer isnot limited to one type and a mixture of two or more other polymers maybe added. The use of plural polymers allows for easy adjustment ofresist properties.

Acid Generator

As the compound which generates an acid in response to actinic light orradiation (B), the resist composition of the invention may furthercomprise (B′) such a compound other than the sulfonium salt compound offormula (4). Component (B′) may be any compound which generates an acidupon exposure to high-energy radiation and specifically, any ofwell-known photoacid generators which are commonly used in prior artresist compositions, especially chemically amplified resistcompositions. Suitable photoacid generators include sulfonium salts,iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, andoxime-O-sulfonate acid generators. Exemplary acid generators are givenbelow while they may be used alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides.

Exemplary sulfonium cations include triphenylsulfonium,(4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 4-methylphenyldiphenylsulfonium,4-tert-butylphenyldiphenylsulfonium, bis(4-methylphenyl)phenylsulfonium,bis(4-tert-butylphenyl)phenylsulfonium, tris(4-methylphenyl)sulfonium,tris(4-tert-butylphenyl)sulfonium, tris(phenylmethyl)sulfonium,2-naphthyldiphenylsulfonium, dimethyl(2-naphthyl)sulfonium,4-hydroxyphenyldimethylsulfonium, 4-methoxyphenyldimethylsulfonium,trimethylsulfonium, 2-oxocyclohexylcyclohexylmethylsulfonium,trinaphthylsulfonium, tribenzylsulfonium, diphenylmethylsulfonium,dimethylphenylsulfonium, 2-oxopropylthiacyclopentanium,2-oxobutylthiacyclopentanium, 2-oxo-3,3-dimethylbutylthiacyclopentanium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, heptafluoropropanesulfonate,nonafluorobutanesulfonate, tridecafluorohexanesulfonate,perfluoro(4-ethylcyclohexane)sulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-(trifluoromethyl)benzenesulfonate, 4-fluorobenzenesulfonate,mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate,toluenesulfonate, benzenesulfonate,4-(p-toluenesulfonyloxy)benzenesulfonate,6-(p-toluenesulfonyloxy)naphthalene-2-sulfonate,4-(p-toluenesulfonyloxy)naphthalene-1-sulfonate,5-(p-toluenesulfonyloxy)naphthalene-1-sulfonate,8-(p-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate,1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-(1-adamantanecarbonyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-tosyloxyethanesulfonate,adamantanemethoxycarbonyldifluoromethanesulfonate,1-(3-hydroxymethyladamantane)methoxycarbonyldifluoromethanesulfonate,methoxycarbonyldifluoromethanesulfonate,1-(hexahydro-2-oxo-3,5-methano-2H-cyclopenta[b]furan-6-yloxycarbonyl)difluoromethanesulfonate,and 4-oxo-1-adamantyloxycarbonyldifluoromethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide,bis(heptafluoropropylsulfonyl)imide, andperfluoro(1,3-propylenebissulfonyl)imide.A typical tris(substituted alkylsulfonyl)methide istris(trifluoromethylsulfonyl)methide. Sulfonium salts based oncombination of the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, heptafluoropropanesulfonate,nonafluorobutanesulfonate, tridecafluorohexanesulfonate,perfluoro(4-ethylcyclohexane)sulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-(trifluoromethyl)benzenesulfonate, 4-fluorobenzenesulfonate,mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate,toluenesulfonate, benzenesulfonate,4-(p-toluenesulfonyloxy)benzenesulfonate,6-(p-toluenesulfonyloxy)naphthalene-2-sulfonate,4-(p-toluenesulfonyloxy)naphthalene-1-sulfonate,5-(p-toluenesulfonyloxy)naphthalene-1-sulfonate,8-(p-toluenesulfonyloxy)naphthalene-1-sulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate,1,1,2,2-tetrafluoro-2-(tetracyclo[6.2.1.1^(3,6).0^(2,7)]dodec-3-en-8-yl)ethanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-(1-adamantanecarbonyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-tosyloxyethanesulfonate,adamantanemethoxycarbonyldifluoromethanesulfonate,1-(3-hydroxymethyladamantane)methoxycarbonyldifluoromethanesulfonate,methoxycarbonyldifluoromethanesulfonate,1-(hexahydro-2-oxo-3,5-methano-2H-cyclopenta[b]furan-6-yloxycarbonyl)difluoromethanesulfonate,and 4-oxo-1-adamantyloxycarbonyldifluoromethanesulfonate.

Exemplary bis(substituted alkylsulfonyl)imides includebis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl)imide,bis(heptafluoropropylsulfonyl)imide, andperfluoro(1,3-propylenebissulfonyl)imide. A typical tris(substitutedalkylsulfonyl)methide is tris(trifluoromethylsulfonyl)methide. Iodoniumsalts based on combination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonylcarbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imidestructures with sulfonates.

Exemplary imide structures are succinimide, naphthalene dicarboxylicacid imide, phthalimide, cyclohexyldicarboxylic acid imide,5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide.

Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonates, 2-nitrobenzyl sulfonates, and 2,6-dinitrobenzyl sulfonates,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin JP 2906999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,

-   bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,-   bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(methanesulfonyl)-α-dimethylglyoxime,-   bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,-   bis-O-(benzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(xylenesulfonyl)-α-dimethylglyoxime,-   bis-O-(trifluoromethanesulfonyl)-nioxime,-   bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,-   bis-O-(10-camphorsulfonyl)-nioxime,-   bis-O-(benzenesulfonyl)-nioxime,-   bis-O-(p-fluorobenzenesulfonyl)-nioxime,-   bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, and-   bis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc. Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethyl-phenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethyl-phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methyl-sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxy-phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethyl-phenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methylsulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoroethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyl-oxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanoneoxime-O-propyl-sulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxy-phenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethanesulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propane-sulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-butanesulfonate). Also included are the oxime sulfonatesdescribed in U.S. Pat. No. 6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxy-imino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenyl-sulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)-phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,

-   α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,-   α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,-   α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,-   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,-   α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,-   α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,-   α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,-   α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,-   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,-   α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,-   α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,-   α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,-   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,-   α-(tosyloxyimino)-3-thienylacetonitrile,-   α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,-   α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,-   α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, and-   α-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the following formula,examples of which are described, for example, in WO 2004/074242.

Herein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group.

Examples include

-   2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-fluorene,-   2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-fluorene,-   2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-fluorene,-   2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxy-imino)-pentyl]-4-biphenyl,-   2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxy-imino)-butyl]-4-biphenyl,    and-   2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyl-oxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,

-   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile,-   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile,-   bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,    etc.

Of these, preferred photoacid generators are sulfonium salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfoniumcamphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butanesulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethylperfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octanesulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene.

In the chemically amplified resist composition, an appropriate amount ofthe photoacid generators (B) and (B′) is, but not limited to, 0.1 to 40parts, and especially 0.1 to 20 parts by weight per 100 parts by weightof the base polymer (i.e., resin component (A) and optional other resincomponent). Too high a proportion of the photoacid generators may giverise to problems of degraded resolution and foreign matter upondevelopment and resist film peeling. Provided that [B] and [B′] standfor the amounts of generators (B) and (B′) added, respectively, thepreferred blending proportion of generators (B) and (B′) is0.1≦[B]/([B]+[B′])≦1, more preferably 0.3≦[B]/([B]+[B′])≦1, and evenmore preferably 0.5≦[B]/([B]+[B′])≦1. If a blending proportion ofgenerator (B) is too low, then exposure dose dependency, pattern densitydependency and/or mask fidelity may be degraded. The photoacidgenerators (B) and (B′) each may be used alone or in admixture of two ormore. The transmittance of the resist film can be controlled by using aphotoacid generator having a low transmittance at the exposurewavelength and adjusting the amount of the photoacid generator added.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is 0 to 2 parts, and especially 0 to 1 part by weight per 100parts by weight of the base polymer. Excessive amounts of theacid-amplifier compound make diffusion control difficult, leading todegradation of resolution and pattern profile.

In addition to components (A) and (B), the resist composition mayfurther comprise (C) an organic solvent and optionally (D) an organicnitrogen-containing compound, (E) a surfactant, and (F) othercomponents.

Organic Solvent

The organic solvent (C) used herein may be any organic solvent in whichthe base resin, acid generator, and additives are soluble. Illustrative,non-limiting, examples of the organic solvent include ketones such ascyclohexanone and methyl amyl ketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate,and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is 200 to 3,000 parts,especially 400 to 2,500 parts by weight per 100 parts by weight of thebase polymer.

Nitrogen-Containing Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as component (D). The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

The organic nitrogen-containing compound used herein may be any ofwell-known organic nitrogen-containing compounds which are commonly usedin prior art resist compositions, especially chemically amplified resistcompositions. Suitable organic nitrogen-containing compounds includeprimary, secondary, and tertiary aliphatic amines, mixed amines,aromatic amines, heterocyclic amines, nitrogen-containing compoundshaving carboxyl group, nitrogen-containing compounds having sulfonylgroup, nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, alcoholicnitrogen-containing compounds, amide derivatives, imide derivatives,carbamate derivatives, and ammonium salts.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, and alcoholicnitrogen-containing compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, and1-cyclohexylpyrrolidone. Suitable imide derivatives include phthalimide,succinimide, and maleimide. Suitable carbamate derivatives includeN-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

Suitable ammonium salts include pyridinium p-toluenesulfonate,triethylammonium p-toluenesulfonate, trioctylammoniump-toluenesulfonate, triethylammonium 2,4,6-triisopropylbenzenesulfonate,trioctylammonium 2,4,6-triisopropylbenzenesulfonate, triethylammoniumcamphorsulfonate, trioctylammonium camphorsulfonate, tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide,benzyltrimethylammonium hydroxide, tetramethylammoniump-toluenesulfonate, tetrabutylammonium p-toluenesulfonate,benzyltrimethylammonium p-toluenesulfonate, tetramethylammoniumcamphorsulfonate, tetrabutylammonium camphorsulfonate,benzyltrimethylammonium camphorsulfonate, tetramethylammonium2,4,6-triisopropylbenzenesulfonate, tetrabutylammonium2,4,6-triisopropylbenzenesulfonate, benzyltrimethylammonium2,4,6-triisopropylbenzenesulfonate, tetramethylammonium acetate,tetrabutylammonium acetate, benzyltrimethylammonium acetate,tetramethylammonium benzoate, tetrabutylammonium benzoate, andbenzyltrimethylammonium benzoate.

Also included are organic nitrogen-containing compounds of the followinggeneral formula (B)-1.N(X)_(n)(Y)_(3-n)  (B)-1In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain an ether or hydroxyl group; and side chain X is independentlyselected from groups of the following general formulas (X1) to (X3), andtwo or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independentlyhydrogen, or straight, branched or cyclic C₁-C₂₀ alkyl groups which maycontain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³is a single bond or a straight or branched C₁-C₄ alkylene group; andR³⁰⁶ is a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀alkylene group which may contain one or more carbonyl, ether, ester orsulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds of imidazolestructure having a polar functional group, represented by the generalformula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogen atom, astraight, branched or cyclic C₁-C₁₀ alkyl group, aryl group or aralkylgroup.

Also included are organic nitrogen-containing compounds of benzimidazolestructure having a polar functional group, represented by the generalformula (B)-8.

Herein, R³¹⁴ is hydrogen, a straight, branched or cyclic C₁-C₁₀ alkylgroup, aryl group or aralkyl group. R³¹⁵ is a polar functionalgroup-bearing, straight, branched or cyclic C₁-C₂₀ alkyl group, and thealkyl group contains as the polar functional group at least one groupselected from among ester, acetal and cyano groups, and may additionallycontain at least one group selected from among hydroxyl, carbonyl,ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently hydrogen, astraight, branched or cyclic C₁-C₁₀ alkyl group or aryl group, or a pairof R³¹⁷ and R³¹⁸ or a pair of R³¹⁹ and R³²⁰ may bond together to form abenzene, naphthalene or pyridine ring with the carbon atoms to whichthey are attached; R³²¹ is hydrogen, a straight, branched or cyclicC₁-C₁₀ alkyl group or aryl group; R³²² and R³²³ each are hydrogen, astraight, branched or cyclic C₁-C₁₀ alkyl group or aryl group, or a pairof R³²¹ and R³²³, taken together, may form a benzene or naphthalene ringwith the carbon atom to which they are attached.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all of hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₇-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring with the carbon atoms to which they are attached.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R³³⁴ and R³³⁵ may bond togetherto form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atomswith the nitrogen atom to which they are attached.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 4 parts, and especially0.01 to 2 parts by weight, per 100 parts by weight of the base polymer.Less than 0.001 part of the nitrogen-containing compound achieves no orlittle addition effect whereas more than 4 parts may result in too low asensitivity.

Other Components

Optionally, the resist composition of the invention may further comprise(E) a surfactant which is commonly used for facilitating the coatingoperation. The surfactant may be added in conventional amounts so longas this does not compromise the objects of the invention.

Illustrative, non-limiting examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (JEMCO Inc.), MegafaceF171, F172, F173, R08, R30, R90 and R94 (DIC Corp.), Fluorad FC-430,FC-431, FC-4430 and FC-4432 (Sumitomo 3M Co., Ltd.), Asahiguard AG710,Surflon S-381, S-382, S-386, SC101, SC102, SC103, SC104, SC105, SC106,KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.); organosiloxanepolymers KP341, X-70-092 and X-70-093 (Shin-Etsu Chemical Co., Ltd.),acrylic acid or methacrylic acid Polyflow No. 75 and No. 95 (KyoeishaUshi Kagaku Kogyo Co., Ltd.). Additional useful surfactants includepartially fluorinated oxetane ring-opened polymers having the structuralformula (surf-1).

It is provided herein that R, Rf, A, B, C, m′, and n′ are applied toonly formula (surf-1), independent of their descriptions other than forthe surfactant. R is a di- to tetra-valent C₂-C₅ aliphatic group.Exemplary divalent groups include ethylene, 1,4-butylene, 1,2-propylene,2,2-dimethyl-1,3-propylene and 1,5-pentylene. Exemplary tri- andtetra-valent groups are shown below.

Herein the broken line denotes a valence bond. These formulae arepartial structures derived from glycerol, trimethylol ethane,trimethylol propane, and pentaerythritol, respectively. Of these,1,4-butylene and 2,2-dimethyl-1,3-propylene are preferably used.

Rf is trifluoromethyl or pentafluoroethyl, and preferablytrifluoromethyl. The letter m′ is an integer of 0 to 3, n′ is an integerof 1 to 4, and the sum of m′ and n′, which represents the valence of R,is an integer of 2 to 4. A is equal to 1, B is an integer of 2 to 25,and C is an integer of 0 to 10. Preferably, B is an integer of 4 to 20,and C is 0 or 1. Note that the above structural formula does notprescribe the arrangement of respective constituent units while they maybe arranged either in blocks or randomly. For the preparation ofsurfactants in the form of partially fluorinated oxetane ring-openedpolymers, reference should be made to U.S. Pat. No. 5,650,483, forexample.

Of the foregoing surfactants, FC-4430, Surflon S-381, KH-20, KH-30, andoxetane ring-opened polymers of formula (surf-1) are preferred. Thesesurfactants may be used alone or in admixture.

In the resist composition, the surfactant is preferably compounded in anamount of up to 2 parts, and especially up to 1 part by weight, per 100parts by weight of the base resin. The amount of the surfactant, ifadded, is preferably at least 0.01 phr.

Optionally, there may be added to the resist composition of theinvention a polymer which will locally segregate at the top of a coatingand functions to adjust a hydrophilic/hydrophobic balance at thesurface, to enhance water repellency, or to prevent low-molecular-weightcomponents from flowing into or out of the coating when the coatingcomes in contact with water or similar liquids. The functional polymermay be added in customary amounts as long as it does not compromise theobjects of the invention.

Preferred examples of the functional polymer which will segregate at thecoating top include polymers and copolymers comprising fluorinated unitsof one or more types, and copolymers comprising fluorinated units andother units. Illustrative examples of suitable fluorinated units andother units are shown below, but not limited thereto.

The functional polymer which will segregate at the coating top shouldpreferably have a weight average molecular weight of 1,000 to 50,000,more preferably 2,000 to 20,000, as measured by GPC versus polystyrenestandards. Outside the range, the polymer may have insufficientsurface-modifying effect or cause development defects. The preferredamount of the functional polymer added is 0 to 10 parts, more preferably0 to 5 parts by weight per 100 parts by weight of the base polymer, andwhen added, at least 1 part by weight.

To the resist composition of the invention, other components such asdissolution regulators, carboxylic acid compounds and acetylene alcoholderivatives may be added if necessary. Optional components may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

The dissolution regulator which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having a carboxyl group include those offormulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl,ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or —(R²⁰⁷)_(h)—COOH (wherein R²⁰⁷ is a straight or branched C₁-C₁₀alkylene), for example, those exemplified for R²⁰¹ and R²⁰², —COOH or—CH₂COOH.

R²⁰⁴ is —(CH₂)_(i)— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom, for example, ethylene,phenylene, carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom, for example, methylene and thoseexemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or aphenyl or naphthyl group in which at least one hydrogen atom issubstituted by a hydroxyl group, for example, hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, hydroxyl-substituted phenyl, andhydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t,s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, ands″+t″=4, and are such that each phenyl structure has at least onehydroxyl group; and α is a number such that the compounds of formula(D8) or (D9) have a weight average molecular weight of from 100 to1,000.

Exemplary acid labile groups on the dissolution regulator include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups in which eachof the alkyls has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkyl groups.Examples of the respective groups are as previously described.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base polymer, and may be usedsingly or as a mixture of two or more thereof. The use of more than 50parts of the dissolution regulator may lead to slimming of the patternedfilm, and thus a decline in resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended.The carboxylic acid compound used herein may be one or more compoundsselected from Groups I and II below, but is not limited thereto.Including this compound improves the PED stability of the resist andameliorates edge roughness on nitride film substrates.

Group I:

Compounds of general formulas (A1) to (A10) below in which some or allof the hydrogen atoms on the phenolic hydroxyl groups are replaced by—R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branched C₁-C₁₀ alkylenegroup), and in which the molar ratio C/(C+D) of phenolic hydroxyl groups(C) to ≡C—COOH groups (D) in the molecule is from 0.1 to 1.0.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl. R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h1)—COOR′ group whereinR′ is hydrogen or —R⁴⁰⁹—COOH.

R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom. R⁴⁰⁶ is a C₁-C₁₀ alkylene, aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom.R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl. R⁴⁰⁸ is hydrogen or methyl.R⁴⁰⁹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹⁰ is hydrogen, astraight or branched C₁-C₈ alkyl or alkenyl, or a —R⁴¹¹—COOH groupwherein R⁴¹¹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹² is hydrogenor hydroxyl.

The letter j is a number from 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6,and are such that each phenyl structure has at least one hydroxyl group;s5 and t5 are numbers which satisfy s5≧0, t5≧0, and s5+t5=5; u1 is anumber from 1 to 4; h1 is a number from 0 to 4; κ is a number such thatthe compound of formula (A6) may have a weight average molecular weightof 1,000 to 5,000; and λ is a number such that the compound of formula(A7) may have a weight average molecular weight of 1,000 to 10,000.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas (AI-1) to (AI-14) and(AII-1) to (AII-10) below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a ≡C—COOH group may be used singly or ascombinations of two or more thereof. The compound having a ≡C—COOH groupis added in an amount ranging from 0 to 5 parts, preferably 0.1 to 5parts, more preferably 0.1 to 3 parts, further preferably 0.1 to 2 partsby weight, per 100 parts by weight of the base polymer. More than 5parts of the compound can reduce the resolution of the resistcomposition.

Preferred examples of the acetylene alcohol derivative which can beadded to the resist composition include those having the general formula(S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industries Ltd.

The acetylene alcohol derivative is preferably added in an amount of 0to 2 parts, more preferably 0.01 to 2 parts, and even more preferably0.02 to 1 part by weight per 100 parts by weight of the base polymer inthe resist composition. More than 2 parts by weight may result in aresist having a low resolution.

Process

Pattern formation using the resist composition of the invention may beperformed by well-known lithography processes. The process generallyinvolves coating, heat treatment (or prebaking), exposure, heattreatment (post-exposure baking, PEB), and development. If necessary,any other steps may be added.

For pattern formation, the resist composition is first applied onto asubstrate (on which an integrated circuit is to be formed, e.g., Si,SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating,Cr, CrO, CrON, MoSi, etc.) by a suitable coating technique such as spincoating, roll coating, flow coating, dip coating, spray coating ordoctor coating. The coating is prebaked on a hot plate at a temperatureof 60 to 150° C. for about 1 to 10 minutes, preferably 80 to 140° C. for1 to 5 minutes. The resulting resist film is generally 0.01 to 2.0 μmthick.

A relationship of a reduced thickness of resist film to an etchselectivity ratio between resist film and processable substrate imposesseverer limits on the process. Under consideration is the tri-layerprocess in which a resist layer, a silicon-containing intermediatelayer, an undercoat layer having a high carbon density and high etchresistance, and a processable substrate are laminated in sequence fromtop to bottom. On etching with oxygen gas, hydrogen gas, ammonia gas orthe like, a high etch selectivity ratio is available between thesilicon-containing intermediate layer and the undercoat layer, whichallows for thickness reduction of the silicon-containing intermediatelayer. A relatively high etch selectivity ratio is also availablebetween the monolayer resist and the silicon-containing intermediatelayer, which allows for thickness reduction of the monolayer resist. Themethod for forming the undercoat layer in this case includes a coatingand baking method and a CVD method. In the case of coating, novolacresins and resins obtained by polymerization of fused ring-containingolefins are used. In the CVD film formation, gases such as butane,ethane, propane, ethylene and acetylene are used. For thesilicon-containing intermediate layer, either a coating method or a CVDmethod may be employed. The coating method uses silsesquioxane,polyhedral oligomeric silsesquioxane (POSS) and the like while the CVDmethod uses silane gases as the reactant. The silicon-containingintermediate layer may have an antireflection function with a lightabsorbing ability and have photo-absorptive groups like phenyl groups,or it may be a SiON film. An organic film may be formed between thesilicon-containing intermediate layer and the photoresist, and theorganic film in this case may be an organic antireflective coating.After the photoresist film is formed, pure water rinsing (orpost-soaking) may be carried out for extracting the acid generator andthe like from the film surface or washing away particles, or aprotective film may be coated.

With a mask having a desired pattern placed above the resist film, theresist film is then exposed to actinic radiation such as UV, deep-UV,electron beams, x-rays, excimer laser light, γ-rays and synchrotronradiation. The exposure dose is preferably about 1 to 200 mJ/cm², morepreferably about 10 to 100 mJ/cm². The film is then baked on a hot plateat 60 to 150° C. for 1 to 5 minutes, preferably 80 to 120° C. for 1 to 3minutes (post-exposure baking=PEB). Thereafter the resist film isdeveloped with a developer in the form of an aqueous base solution, forexample, 0.1 to 5 wt %, preferably 2 to 3 wt % aqueous solution oftetramethylammonium hydroxide (TMAH) for 0.1 to 3 minutes, preferably0.5 to 2 minutes by conventional techniques such as dip, puddle or spraytechniques. In this way, a desired resist pattern is formed on thesubstrate. It is appreciated that the resist composition of theinvention is suited for micropatterning using such high-energy radiationas deep UV with a wavelength of 254 to 193 nm, vacuum UV with awavelength of 157 nm, electron beams, soft x-rays, x-rays, excimer laserlight, γ-rays and synchrotron radiation, and best suited formicropatterning using high-energy radiation in the wavelength range of180 to 200 nm.

Immersion lithography can be applied to the resist composition of theinvention. The ArF immersion lithography uses a liquid having arefractive index of at least 1 and transparent to exposure radiation,such as pure water or alkanes as the immersion solvent. The immersionlithography involves prebaking a resist film and exposing the resistfilm to light through a projection lens, with pure water or similarliquid interposed between the resist film and the projection lens. Sincethis allows projection lenses to be designed to a numerical aperture(NA) of 1.0 or higher, formation of finer patterns is possible. Theimmersion lithography is important for the ArF lithography to survive tothe 45-nm node, with a further development thereof being accelerated. Inthe case of immersion lithography, pure water rinsing (or post-soaking)may be carried out after exposure for removing water droplets left onthe resist film, or a protective coating may be applied onto the resistfilm after pre-baking for preventing any dissolution from the resist andimproving water slip on the film surface. The resist protective coatingused in the immersion lithography is preferably formed from a solutionof a polymer having 1,1,1,3,3,3-hexafluoro-2-propanol residue which isinsoluble in water and soluble in an alkaline developer liquid, in asolvent selected from alcohols of at least 4 carbon atoms, ethers of 8to 12 carbon atoms, and mixtures thereof.

The technique enabling the ArF lithography to survive to the 32-nm nodeis a double patterning process. The double patterning process includes atrench process of processing an underlay to a 1:3 trench pattern by afirst step of exposure and etching, shifting the position, and forming a1:3 trench pattern by a second step of exposure, for forming a 1:1pattern; and a line process of processing a first underlay to a 1:3isolated left pattern by a first step of exposure and etching, shiftingthe position, processing a second underlay formed below the firstunderlay by a second step of exposure through the 1:3 isolated leftpattern, for forming a half-pitch 1:1 pattern.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. Mw is a weight average molecular weight asmeasured by gel permeation chromatography (GPC) versus polystyrenestandards.

Preparation of Resist Material

Examples

Positive resist compositions were prepared by dissolving a polymer, acidgenerator, and basic compound in a solvent in accordance with theformulation shown in Table 1 and filtering through a Teflon® filter witha pore size of 0.2 μm. In all runs, the solvent contained 0.005 wt % ofsurfactant KH-20 (Asahi Glass Co., Ltd.).

TABLE 1 Acid Resist Resin generator Base Solvent 1 Solvent 2 R-01 P-01(80) PAG-1 (10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-02 P-02 (80)PAG-1 (10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-03 P-03 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-04 P-04 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-05 P-05 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-06 P-06 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-07 P-07 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-08 P-08 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-09 P-09 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-10 P-10 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-11 P-11 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-12 P-12 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-13 P-13 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-14 P-14 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-15 P-15 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-16 P-16 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-17 P-17 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-18 P-18 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-19 P-19 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-20 P-20 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-21 P-21 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-22 P-22 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-23 P-01 (80) PAG-2(11.0) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-24 P-01 (80) PAG-3(10.0) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-25 P-01 (80) PAG-4(10.2) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-26 P-01 (80) PAG-5(12.6) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-27 P-01 (80) PAG-6(10.4) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-28 P-22 (80) PAG-2(11.0) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-29 P-22 (80) PAG-3(10.0) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-30 P-22 (80) PAG-4(10.2) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-31 P-22 (80) PAG-5(12.6) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-32 P-22 (80) PAG-6(10.4) Base-1 (1.41) PGMEA (1,120) CyHO (480) The values in parenthesesare in parts by weight.Comparative Examples

Resist compositions for comparison were prepared by the same procedureas in Examples aside from using the formulation shown in Table 2.

TABLE 2 Acid Resist Resin generator Base Solvent 1 Solvent 2 R-33 P-23(80) PAG-1 (10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-34 P-24 (80)PAG-1 (10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-35 P-25 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) R-36 P-26 (80) PAG-1(10.1) Base-1 (1.41) PGMEA (1,120) CyHO (480) The values in parenthesesare in parts by weight.

In Tables 1 and 2, the base and solvent are designated by abbreviations,which have the following meaning.

-   Base-1: tri(2-methoxymethoxyethyl)amine-   PGMEA: propylene glycol monomethyl ether acetate-   CyHO: cyclohexanone

The resins designated by abbreviations are polymers constructed as inTables 3 to 6.

TABLE 3 Resin Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Mw P-01 A-1M (0.30)B-1M (0.25) C-4M (0.45) 7,000 P-02 A-2M (0.30) B-1M (0.25) C-4M (0.45)6,200 P-03 A-3M (0.30) B-1M (0.25) C-4M (0.45) 7,200 P-04 A-4M (0.30)B-1M (0.25) C-4M (0.45) 6,500 P-05 A-5M (0.30) B-1M (0.25) C-4M (0.45)6,900 P-06 A-6M (0.30) B-1M (0.25) C-4M (0.45) 7,200 P-07 A-1M (0.30)B-1M (0.25) C-4A (0.45) 6,700 P-08 A-1M (0.30) B-2M (0.25) C-4M (0.45)7,100 P-09 A-1M (0.30) B-3M (0.25) C-4M (0.45) 7,300 P-10 A-1M (0.30)B-4M (0.25) C-4M (0.45) 6,900 P-11 A-1M (0.30) B-1M (0.25) C-1M (0.45)6,700 P-12 A-1M (0.30) B-1M (0.25) C-2M (0.45) 6,800 P-13 A-1M (0.30)B-1M (0.25) C-3M (0.45) 7,100 P-14 A-1M (0.30) B-1M (0.25) C-2M (0.35)C-5M (0.10) 7,000 P-15 A-1M (0.30) B-1M (0.25) C-2M (0.35) C-6M (0.10)7,000 P-16 A-1M (0.30) B-1M (0.25) C-2M (0.35) C-7M (0.10) 6,900 P-17A-1M (0.25) B-1M (0.25) C-4M (0.40) C-8M (0.10) 6,500 P-18 A-1M (0.25)B-1M (0.25) C-4M (0.40) C-9M (0.10) 6,600 P-19 A-1M (0.25) B-1M (0.25)C-4M (0.40) C-10M (0.10) 6,500 P-20 A-1M (0.25) B-1M (0.25) C-4M (0.40)C-11M (0.10) 6,200 P-21 A-1M (0.20) A-4M (0.10) B-1M (0.25) C-2M (0.35)C-6M (0.10) 6,800 P-22 A-1M (0.20) A-4M (0.10) B-1M (0.25) C-2M (0.35)C-7M (0.10) 6,600 P-23 A-1M (0.30) B-5M (0.25) C-4M (0.45) 6,900 P-24A-1M (0.30) B-6M (0.25) C-4M (0.45) 6,700 P-25 A-1M (0.25) B-5M (0.25)C-4M (0.40) C-9M (0.10) 6,500 P-26 A-1M (0.20) A-4M (0.10) B-6M (0.25)C-2M (0.35) C-7M (0.10) 6,400 The value in parentheses is anincorporation ratio of a particular unit expressed in molar ratio.

TABLE 4

A-1M (R = CH₃) A-2M (R = CH₃) A-1A (R = H) A-2A (R = H)

A-3M (R = CH₃) A-4M (R = CH₃) A-3A (R = H) A-4A (R = H)

A-5M (R = CH₃) A-6M (R = CH₃) A-5A (R = H) A-6A (R = H)

TABLE 5

B-1M (R = CH₃) B-2M (R = CH₃) B-3M (R = CH₃) B-1A (R = H) B-2A (R = H)B-3A (R = H)

B-4M (R = CH₃) B-5M (R = CH₃) B-4A (R = H) B-5A (R = H)

B-6M (R = CH₃) B-6A (R = H)

TABLE 6

C-1M (R = CH₃) C-2M (R = CH₃) C-1A (R = H) C-2A (R = H)

C-3M (R = CH₃) C-4M (R = CH₃) C-3A (R = H) C-4A (R = H)

C-5M (R = CH₃) C-6M (R = CH₃) C-5A (R = H) C-6A (R = H)

C-7M (R = CH₃) C-8M (R = CH₃) C-7A (R = H) C-8A (R = H)

C-9M (R = CH₃) C-10M (R = CH₃) C-9A (R = H) C-10A (R = H)

C-11M (R = CH₃) C-11A (R = H)

The acid generators designated by abbreviations in Tables 1 and 2 aresulfonium salts shown in Table 7.

TABLE 7 PAG-1

PAG-2

PAG-3

PAG-4

PAG-5

PAG-6

Resolution TestExamples 1 to 32 and Comparative Examples 1 to 4

On silicon wafers having an antireflective coating (ARC29A, NissanChemical Industries Ltd.) of 78 nm thick, the resist compositions (R-01to 32) of the invention and comparative resist compositions (R-33 to 36)were spin coated, then baked at 100° C. for 60 seconds to give resistfilms having a thickness of 120 nm. Using an ArF excimer laser stepper(Nikon Corp., NA 0.85), the resist films were exposed, baked (PEB) for60 seconds and then puddle developed for 30 seconds with a 2.38 wt %aqueous solution of tetramethylammonium hydroxide. In this way, 1:1line-and-space patterns and 1:10 isolated line patterns were formed. ThePEB step used an optimum temperature for a particular resistcomposition.

The pattern-bearing wafers were observed under a top-down scanningelectron microscope (TDSEM). The optimum exposure was an exposure dose(mJ/cm²) which provided a 1:1 resolution at the top and bottom of a80-nm 1:1 line-and-space pattern. The maximum resolution of the resistwas defined as the minimum line width (on-mask size, in increments of 5nm) of a 1:1 line-and-space pattern that was found resolved andseparated at the optimum exposure, with smaller values indicating betterresolution. The 1:10 isolated line pattern at the optimum exposure wasalso observed for determining an actual on-wafer size of the isolatedline pattern with an on-mask size of 140 nm, which was reported as maskfidelity (on-wafer size, a larger size being better). The patternprofile was visually observed to see whether or not it was rectangular.

Tables 8 and 9 tabulate the test results (maximum resolution, maskfidelity, and profile) of the inventive and comparative resistcompositions, respectively.

TABLE 8 Optimum Maximum Mask PEB temp., exposure, resolution, fidelity,Example Resist ° C. mJ/cm² nm nm Pattern profile 1 R-01 105 42 70 95rectangular 2 R-02 110 41 70 89 rectangular 3 R-03 115 44 70 94 somewhatT-top 4 R-04 110 42 70 98 rectangular 5 R-05 100 40 70 90 rectangular 6R-06 115 43 70 96 rectangular 7 R-07 100 38 75 85 somewhat rounded top 8R-08 105 43 70 94 rectangular 9 R-09 105 40 70 93 rectangular 10 R-10105 39 70 91 rectangular 11 R-11 95 45 70 93 rectangular 12 R-12 95 4170 95 rectangular 13 R-13 105 43 70 90 somewhat T-top 14 R-14 95 42 7093 rectangular 15 R-15 95 42 70 95 rectangular 16 R-16 95 43 70 94rectangular 17 R-17 105 40 70 92 somewhat rounded top 18 R-18 105 42 7094 rectangular 19 R-19 105 40 75 88 rectangular 20 R-20 105 40 70 97rectangular 21 R-21 95 42 70 95 rectangular 22 R-22 95 43 70 95rectangular 23 R-23 105 47 70 98 rectangular 24 R-24 105 44 70 98rectangular 25 R-25 105 44 70 96 rectangular 26 R-26 115 42 70 95rectangular 27 R-27 105 43 70 96 rectangular 28 R-28 95 47 70 99rectangular 29 R-29 95 45 70 98 rectangular 30 R-30 95 44 70 98rectangular 31 R-31 105 43 70 97 rectangular 32 R-32 95 44 70 97rectangular

TABLE 9 Optimum Maximum Mask Comparative PEB temp., exposure,resolution, fidelity, Example Resist ° C. mJ/cm² nm nm Pattern profile 1R-33 105 34.0 75 80 rectangular 2 R-34 105 32.0 75 78 somewhat roundedtop 3 R-35 105 32.0 75 78 rectangular 4 R-36 95 33.0 75 81 rectangular

It is seen from the results of Table 8 that the resist compositionswithin the scope of the invention exhibit excellent resolutionperformance, mask fidelity, and satisfactory pattern profiles. Incontrast, Table 9 reveals that Comparative Examples 1 to 4, which useprior art resins, are inferior in maximum resolution and mask fidelity.It has been demonstrated that a resist composition which uses a polymercomprising specific recurring units as a base resin is improved inresolution performance, as compared with resist compositions of theprior art design.

Japanese Patent Application No. 2008-227727 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A positive resist composition comprising (A) a resin component whichbecomes soluble in an alkaline developer under the action of an acid and(B) a compound capable of generating an acid in response to actiniclight or radiation, wherein said resin component (A) is a polymercomprising recurring units containing a non-leaving hydroxyl group,represented by the general formula (1):

wherein R¹ is hydrogen, methyl or trifluoromethyl, and m is 1 or 2, withthe proviso that the number “m” of hydroxyl groups each attach to atertiary carbon atom.
 2. The composition of claim 1 wherein the polymeras resin component (A) further comprises recurring units of the generalformulae (2) and (3):

wherein R¹ is each independently hydrogen, methyl or trifluoromethyl, R²is an acid labile group, and R³ is a group containing a 5- or 6-memberedlactone ring as a partial structure.
 3. The composition of claim 1wherein said compound (B) is a sulfonium salt compound having thegeneral formula (4):

wherein R⁴, R⁵ and R⁶ are each independently hydrogen or a straight,branched or cyclic, monovalent hydrocarbon group of 1 to 20 carbon atomswhich may contain a heteroatom, R⁷ is a straight, branched or cyclic,monovalent hydrocarbon group of 7 to 30 carbon atoms which may contain aheteroatom, and R⁸ is hydrogen or trifluoromethyl.
 4. A process forforming a pattern, comprising the steps of applying the positive resistcomposition of claim 1 onto a substrate to form a resist coating, heattreating, exposing the resist coating to high-energy radiation orelectron beam through a photomask, heat treating, and developing theexposed coating with a developer.
 5. A process for forming a pattern,comprising the steps of applying the positive resist composition ofclaim 1 onto a substrate to form a resist coating, heat treating,exposing the resist coating to high-energy radiation or electron beamthrough a photomask, heat treating, and developing the exposed coatingwith a developer, the exposing step being effected by the immersionlithography wherein a high refractive index liquid having a refractiveindex of at least 1.0 intervenes between the resist coating and aprojection lens.
 6. A process for forming a pattern, comprising thesteps of applying the positive resist composition of claim 1 onto asubstrate to form a resist coating, heat treating, exposing the resistcoating to high-energy radiation or electron beam through a photomask,heat treating, and developing the exposed coating with a developer, saidprocess further comprising the step of applying a protective coating onthe resist coating, the exposing step being effected by the immersionlithography wherein a high refractive index liquid having a refractiveindex of at least 1.0 intervenes between the protective coating and aprojection lens.